An electric motor drive device for driving a motor generator used in a hybrid vehicle or the like converts power from a DC power supply to AC power and supplies power to the electric motor. In this power conversion device, semiconductor switching elements such as MOSFET (metal oxide silicon field effect transistor) are used, whereby high-speed application is achieved. For using semiconductor switching elements, switching loss increases with increase in the switching frequency due to the high-speed application, resulting in reduction in efficiency of the power conversion device.
To solve the above problem, an electric motor drive device is proposed in which an additional circuit is provided between a DC power supply and an inverter circuit so as to have a soft-switching function of suppressing switching loss when an inverter main circuit element is turned on (for example, Patent Document 1).